Self-propelled suction cleaners are customarily used for cleaning the submerged surfaces of pools and in particular, swimming pools having various surface finishes and contoured shapes. Various techniques have been employed in the mechanisms that drive these self-propelled cleaners. Three of the more common mechanisms use either a shut off valve, turbine drive or drive wheels. In some cases, combinations of these mechanisms are used.
The U.S. Pat. No. 4,536,908 issued to Johann N. Raubenheimer on Aug. 27, 1985 discloses a suction cleaner for a swimming pool that is supported on a bogie or truck assembly with inclined supporting feet. The bogie assembly is mechanically rocked by means of a turbine through which water is pulled by suction to cause the cleaner to move. In order to change the direction of path of the cleaner, a second turbine drives a hose connection at the top of the cleaner in opposite directions with long periods of dwell in between. In other words, the device is continuously driven in the forward or turning directions.
A turbine driven swimming pool cleaner is also disclosed in the U.S. Pat. No. 4,939,806 issued to Carl F. Supra on Jul. 10, 1990. In this Supra device, a cleaner having a head is mounted on wheels. There is a suction passage and a propeller which is driven by the turbine and which propels the head. A rudder, which is oscillated via a gear train driven by the turbine, is used to vary the direction of movement of the head.
A turbine and wheel styled device is disclosed in the U.S. Pat. No. 5,099,535 issued on Mar. 31, 1992 to Daniel J. V. D. Chauvier, Cleaner for Submerged Surfaces. In this Chauvier device, a cleaner for a submerged surface comprises a body that defines a suction passage and pressure passage. The suction passage extends between an inlet and outlet in the body and is connectable to the inlet of a filtration system by flexible hose. A second hose connects the inlet on the device to an outlet of the system. Water flowing under pressure to the inlet drives a turbine which in turn drives hind wheels to displace the apparatus over the surface while debris or the like is sucked up through the suction passage and out through the hose that is attached to the filtration system. The suction and return hoses are those of the flexible kind typically used in swimming pool cleaning systems.
In the U.S. Pat. No. 4,208,752 issued to Helmut J. Hofmann on Jun. 24, 1980, an apparatus for cleaning swimming pools in a stepwise movement over the pool walls comprises a balanced operating head having an inlet and an outlet, the outlet adapted to be swivelably connected to a longitudinally resilient and flexible suction hose. The inlet axis is inclined at an angle to that of the outlet. A passage extends through the head from inlet to outlet, and an oscillator valve in the head is adapted to alternately open and close said passage. A baffle plate is disposed in the head between the inlet and valve to form a restricted suction connection between inlet and outlet around the valve when the passage is closed. The flow of water causes the valve to oscillate between its two terminal positions. In one position, the flow is full and direct through the opening and passage to the outlet. In the other position of the valve, there is a maximum reduction in liquid flow through the head. This results in an intermittent cut off flow through the head as the valve oscillates between its terminal positions, and this in turn causes pulsation which result in longitudinal contractions and relaxations in the longitudinally resilient suction pipe from the head to the outlet from the swimming pool to its filter unit. In consequence of these contractions and relaxations and a simultaneous reduction and increase of the force applied to hold the cleaning head disc against the surface to be cleaned, a step by step movement of the head takes place over the surface to be cleaned.
The U.S. Pat. No. 4,807,318 issued to Dieter H. F. Kallenbach on Feb. 28, 1989, Suction Operated Cleaner, an automatic pool cleaner is disclosed which also operates on the interruption of an induced flow of water through the cleaner. The interruption in the flow of water drawn through the pool cleaner is used to provide a propulsive force to cause the cleaner to move over submerged pool surfaces. The control of the interruption is effected through a tubular axially resilient diaphragm one end of which is closed and adapted to hold normally closed a passage from the head of the pool cleaner to the usual form of flexible hose connecting the pool cleaner to the filtration unit. The flow of water through the pool cleaner causes a suction in a passageway greater than that in a connection, the result being that a spring and diaphragm force the closure of the passageway. The intermittent interruption of flow through the passageway and hose, and the simultaneous release of the force holding the cleaner and disc against the submerged surface causes the cleaner to move in a stepwise manner over the surface to be cleaned.
In addition to the mechanism used to move the cleaning device along the submerged surface to be cleaned, various appendages have been added to these devices to provide some control over the cleaning pattern and for control of the cleaner when encountering obstacles such as abrupt surface changes and exiting the submersible fluid in which they were designed to operate. The art of submersible pool cleaners has been open to these various methods of automatically propelling the cleaner over the surfaces to be cleaned because any one brings inherent problems with its design.
In cleaning devices using shut off valves, the valve intake tends to clog with larger debris and in order to correct this condition, the cleaning device must be removed from the pool and disassembled for cleaning. The membranes used in these units have a tendency to break and require replacement. The dramatic reduction of flow needed to create the step by step movement of the cleaning device results in severe changes in the pressure head at the suction pump thus placing additional wear on this pump and motor. Cleaning devices using turbine styled systems must depend on the high speed movement of the turbine, large number of bearings and the needed multitude of parts to convert the high speed to the relatively slow cleaning movement. In addition, the many bearing surfaces perform poorly after performance in the sand which grinds down the bearing parts. The cleaning devices relying on wheels for their traction encounter problems when climbing the vertical walls of typical swimming pools. The wheels slip in attempting to maneuver on the vertical wall and will slip under certain conditions when climbing from the deep end to the shallow end of the pool.
Many of the devices used tend to follow an established pattern once placed into operation. This pattern, often a figure eight style, tends therefore to avoid certain areas over others that see the cleaner more often than necessary. Finally, the onset of new plastics and fiberglass surfaces for swimming pools has created the added demand on these devices to be able to maneuver over slippery surfaces not before encountered. The goal in the art is to find that device which will cover the desired submerged surfaces, be able to execute vertical walls, escape obstacles, avoid climbing out of the submersible fluid where the sucking in of air will cause damage and interrupt operation, place a minimum of excess demand on the system suction pump and motor, and have as few failing parts as possible.